1. Field of the Invention
The present invention relates to an image sensor device which comes in contact with an image to be read and converts optical image information into electric signals, and an image sensor unit in which the image sensor device is used, as well as methods for producing the same. More specifically, the present invention relates to a direct-contact type image sensor device that can be suitably used in a facsimile, an image reader, etc., which image sensor device comes in complete contact with an original to be read so as to read image information in a vertical direction with respect to a direction in which the original is conveyed, and an image sensor unit in which the image sensor device is used, as well as methods for producing the same.
2. Description of the Related Art
As image sensors which convert one-dimensional image information into electric signals, there have been realized reduction-type image sensors including a one-dimensional CCD (Charge Coupled Device), one-dimensional image sensors including a long-size sensor which conducts neither magnification nor reduction, and the like. Such conventional image sensors have been put on the market. A one-dimensional image sensor including a long-size sensor has such excellent features as high utilization efficiency of light, high-speed reading, and the small size of whole optical system. Such an image sensor is categorized into a contact type image sensor, which includes an array of convergence-type lot lenses, and a direct-contact type image sensor, which includes no optical lenses. The direct-contact type image sensor can be fabricated at low cost, since no array of convergence-type lot lenses is required therein. Moreover, the direct-contact type image sensor can easily be realized in a small size.
FIG. 8 shows a conventional direct-contact type image sensor device. As is shown in FIG. 8, the image sensor device includes a light-transmitting substrate 61 on which a circuit conductor layer 62 is formed. An image sensor chip 63 is mounted face-down on, by way of a transparent insulating resin layer the upper surface of the light-transmitting substrate 61. A flip-chip-bonding method is used in mounting the image sensor chip 63. On the lower surface of the light-transmitting substrate 61, a transparent electrically conductive layer 68 is formed. A transparent protection layer 66 is formed over the light-transmitting substrate 61 so as to cover the image sensor chip 63. The image sensor chip 63 includes a light-sensitive element array 67 and electrodes 64, which are in contact with the circuit conductor layer 62. A light source 70 radiates a light beam on an original 71 through the transparent insulating resin layer 65, the light-transmitting substrate 61, and the transparent conductive layer respectively, (In the present specification, the term "original" refers to any material on which optical information is carried. The optical information may be written, printed, painted, copied, etc. on the original.) The light beam is reflected from the original 71 so as to be received by the light-sensitive element array 67 by way of the transparent conductive layer 68, the light-transmitting substrate 81, and the transparent insulating resin layer 65.
Each of the transparent insulating resin layer 65, the light-transmitting substrate 81, and the transparent conductive layer 68 must have e certain thickness in order that the image sensor device has sufficient physical strength. However, there is a problem that optical crosstalk occurs within the light-transmitting substrate 61 as well as other places when the thicknesses of the transparent insulating resin layer 65, The light-transmitting substrate 61, and the transparent conductive layer 68 are increased, since the distance between the light-sensitive element array 67 and the original 71 is increased. Such optical crosstalk decreases the MTF (Modulation Transfer Function) value and/or the resolution of the image sensor device.
FIG. 9 shows a conventional direct-contact type image sensor device obtained by further providing a light-interrupting layer 60 for the image sensor device shown in FIG. 8. The light-interrupting layer 60 is formed on the upper surface of a light-transmitting substrate 61. The light-interrupting layer 60 partially interrupts a light beam which is emitted from a light source 70 disposed obliquely above the light-transmitting substrate 61 and is radiated on an original 71 through a transparent protection layer 66, a transparent insulating resin layer 65, and the light-transmitting substrate 61. By providing the light-interrupting layer 60, an unnecessary portion of light entering from above is interrupted. As a result, flares and crosstalk can be reduced.